Silver halide emulsions are typically prepared by precipitating silver halide (silver bromide, silver iodide, silver chloride or mixture thereof) in the presence of a hydrophilic colloid (normally gelatin). Silver halide emulsions are then typically subjected to a sensitization process for increasing their sensitivity to light. The sensitization process mainly involves spectral sensitization and chemical sensitization. Spectral sensitization includes the addition of spectral sensitizing dyes which can be adsorbed on the silver halide grain surface in order to make the emulsion sensitive to a particular wavelength radiation, such as visible or infrared radiation. Chemical sensitization includes the addition of various compounds to obtain a prescribed value of sensitivity and contrast. Typical methods for chemical sensitizing a silver halide photographic emulsion include sulfur sensitization, noble metal sensitization, and reduction sensitization. It is also common to have a combination of chemical sensitizing methods, such as sulfur-noble metal sensitization, reduction-noble metal sensitization, and the like, all which have been previously described. See, e.q., Research Disclosure, September 1994, Item 36544, Paragraph IV, pp. 510-511, which lists a wide array of references for each of the above-mentioned methods.
In recent years, there has been a strong demand for high sensitivity, low graininess and low fog in a silver halide photographic element as well as for rapid processing in which development is expedited. Various improvements in the above sensitizing methods have been made.
One approach focuses on the addition of coating aids. After the sensitization process, the silver halide emulsion is coated on a support together with coating additives. A description of useful coating aids can be found in Research Disclosure No. 38597, September 1996, "Photographic Silver Halide Emulsions, Preparations, Addenda, Systems and Processing", Item IX.
Useful coating aids including hydroxy-substituted aryl compounds are known. For example, U.S. Pat. No. 5,028,520 (Ito Tadashi, Silver Halide Photographic Material For X-Ray Use) describes the use of hydroquinone sulfonic acid potassium salt on tabular silver halide emulsion in an amount of from 0.03 to 0.5 moles per mole of silver to decrease the surface glossiness.
JP 54-040729, JP 56-001936 and JP 62-021143 describe the use of polyhydroxybenzene derivatives on cubic silver halide emulsions to decrease pressure sensitivity in graphic art films.
EP 452772, EP 476521, EP 482599 and EP 488029 describe the use of polyhydroxybenzene derivatives with functional groups that allow better silver halide grain adsorption to decrease pressure sensitivity of final film.
EP 339870 describes a silver halide photographic emulsion having in reactive association a sensitizing amount of polyalkylene glycol compound and a fog reducing amount of an arylhydroxy compound.
European Patent Application No. 97-116341.5 describes the use of aryl derivative in a process to prepare a silver halide emulsion to improve the speed to Dmin ratio of the resulting photographic elements.
Other useful known coating aids are olysaccharides. For example, U.S. Pat. No. 5,374,509 (Valentini Jose, Photographic Element Containing A Binder Composition For Improved Drying Characteristics) describes a mixture of hydrophilic colloid, a branched polysaccharide, a polyacrylamide, a polyvinylidine chloride and a polyacrylate in a quick water absorb and water release binder.
JP 8-0122956 describes a silver halide emulsion which contains a metal chelating agent (type tartaric acids, ethylene diamine tetraacetates, nitro triacetates, uramil diacetates) and a mono-, a di- or a polysaccharide. The silver halide emulsion has high sensitivity.
JP 55098745, JP 55098746, describes polysaccharides having glucose units as main chain, and mannose, fucose and glucoronic acids as side chain in photographic solution preparation for high speed coating and improved physical properties.
U.S. Pat. No. 5,370,986 (Lok et. al., Stabilization Of Photographic Recording Materials) describes the use of polyhydroxyalkyl stabilizer compounds and a co-stabilizing agent in silver chloride photographic element to prevent fog formation. The polyhydroxyalkyl stabilizer is a non-reducing oligosaccharide or its alkyl-substituted glycoside of formula R--(CHOH).sub.n (CHOR1).sub.m --Z with n=3-7, m=0-7, R.dbd.R1.dbd.H OR 1-3C alkyl, Z.dbd.COOR' or CONR'R' and R'.dbd.1-3C alkyl.